Method and apparatus for channel access in wireless communication system

ABSTRACT

A communication method for a channel access in a wireless communication system and an apparatus therefor are provided. The communication method includes an evolved NodeB (eNB) that transmits data to a user equipment (UE) through a licensed band, and determines whether an unlicensed band channel is in an idle state during a first channel sensing duration. If the unlicensed band channel is in the idle state, the eNB transmits data to the UE through an unlicensed band during a first channel occupying duration, a second channel sensing duration, and a second channel occupying duration. In the method, a sum of the first channel occupying duration, the second channel sensing duration, and the second channel occupying duration is equal to or less than a certain time.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/429,919, filed on Feb. 10, 2017, which has issued as U.S. Pat.No. 10,257,764 on Apr. 9, 2019 and was based on and claims the benefitunder 35 U.S.C. § 119(e) of a U.S. Provisional application filed on Feb.15, 2016 in the U.S. Patent and Trademark Office and assigned Ser. No.62/295,476, the entire disclosure of which is hereby incorporated byreference.

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for a channelaccess in a wireless communication system.

BACKGROUND

A recent mobile communication system is evolving into a high-speed andhigh-quality wireless packet data communication system for providing adata service and a multimedia service, outgrowing an initialvoice-oriented service. In order to support such a high-speed andhigh-quality wireless packet data transfer service, various mobilecommunication standards such as high speed downlink packet access(HSDPA), high speed uplink packet access (HSUPA), long term evolution(LTE), and LTE advanced (LTE-A) of 3rd generation partnership project(3GPP), high rate packet data (HRPD) of 3GPP2, and 802.16 of Instituteof Electrical and Electronics Engineers (IEEE) have been developed. Inparticular, LTE/LTE-A/LTE-A Pro (hereinafter LTE) continues to developand evolve standards to improve system capacity and frequencyefficiency.

Typically, the LTE system can greatly increase a data transfer rate andsystem capacity by using carrier aggregation (CA) technology capable ofoperating the system using a plurality of frequency bands. In addition,the frequency band currently used in the LTE system is generally alicensed band (licensed spectrum or licensed carrier) used by anoperator having authority.

However, since a typical frequency band (e.g., a frequency band of 5 GHzor less) that provides a mobile communication service has been alreadyoccupied by another operator or another communication system, anoperator may often fail to obtain a number of licensed band frequenciesand thus have difficulty in expanding the system capacity by using theCA technology.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method in which a user equipment (UE)transmits an uplink data channel through one or more uplink subframes byusing uplink transmission setting information received from an evolvedNodeB (eNB).

However, the present disclosure is not limited to the above aspects, andany other aspect, even though not mentioned herein, may be wellunderstood from the following description.

Another aspect of the present disclosure is to provide a method in whichthe UE transmits an uplink data channel through one or more uplinksubframes by using uplink transmission setting information received fromthe eNB in case of transmitting the uplink data channel at an unlicensedband.

Additionally, an embodiment of the present disclosure includes, if amaximum occupancy time of the eNB or the UE defined at a channel accesspriority is greater than a time defined by a regional or nationalregulation in a mobile communication system that operates in anunlicensed band, determining that an unlicensed band channel is an idlechannel, through a channel sensing operation performed during a channelsensing duration established according to the channel access priority,occupying the channel during the time defined by the regional ornational regulation, and further occupying the channel through anadditional channel sensing duration.

In accordance with an aspect of the present disclosure, a communicationmethod of eNB is provided. The method includes transmitting data to UEthrough a licensed band, determining whether an unlicensed band channelof an unlicensed band is in an idle state during a first channel sensingduration, and if the unlicensed band channel is in the idle state,transmitting data to the UE through the unlicensed band during a firstchannel occupying duration, a second channel sensing duration, and asecond channel occupying duration. In this method, a sum of the firstchannel occupying duration, the second channel sensing duration, and thesecond channel occupying duration may be equal to or less than a certaintime.

In the method, the certain time may be determined, based on a roundingvalue of a result of a calculation between a maximum occupancy time forthe eNB or the UE to occupy the unlicensed band and an actual occupancytime for the eNB or the UE to occupy the unlicensed band.

In the method, the calculation may include dividing the maximumoccupancy time by the actual occupancy time and then subtracting one.

In the method, the certain time may be determined according to1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (us) in which T_(mcot)denotes a maximum occupancy time for the eNB or the UE to occupy theunlicensed band, T_(j) denotes an actual occupancy time for the eNB orthe UE to occupy the unlicensed band, and T_(js) denotes a length of thesecond channel sensing duration.

In the method, the second channel sensing duration may include an idleslot duration having 16 us and two channel sensing slot durations eachhaving 9 us.

In accordance with another aspect of the present disclosure, acommunication method of UE is provided. The method includes receivingdata from eNB through a licensed band, and if an unlicensed band channelof an unlicensed band is in an idle state during a first channel sensingduration, receiving data from the eNB through the unlicensed band duringa first channel occupying duration, a second channel sensing duration,and a second channel occupying duration. In this method, a sum of thefirst channel occupying duration, the second channel sensing duration,and the second channel occupying duration may be equal to or less than acertain time.

In accordance with another aspect of the present disclosure, an eNB isprovided. The eNB includes a transceiver configured to transmit orreceive a signal, and a controller configured to control the transceiverto transmit data to UE through a licensed band, to determine whether anunlicensed band channel of an unlicensed band is in an idle state duringa first channel sensing duration, and if the unlicensed band channel isin the idle state, to control the transceiver to transmit data to the UEthrough the unlicensed band during a first channel occupying duration, asecond channel sensing duration, and a second channel occupyingduration. In this eNB, a sum of the first channel occupying duration,the second channel sensing duration, and the second channel occupyingduration may be equal to or less than a certain time.

In accordance with another aspect of the present disclosure, a UE isprovided. The UE includes a transceiver configured to transmit and/orreceive a signal, and a controller configured to control the transceiverto receive data from eNB through a licensed band, and if an unlicensedband channel of an unlicensed band is in an idle state during a firstchannel sensing duration, to control the transceiver to receive datafrom the eNB through the unlicensed band during a first channeloccupying duration, a second channel sensing duration, and a secondchannel occupying duration. In this UE, a sum of the first channeloccupying duration, the second channel sensing duration, and the secondchannel occupying duration may be equal to or less than a certain time.

According to the present disclosure, it is possible to effectivelyperform a channel occupancy operation for using an unlicensed band andalso improve coexistence performance between devices using theunlicensed band by clearly setting a threshold as to the channeloccupancy operation.

In accordance with another aspect of the present disclosure, a method inwhich UE transmits an uplink data channel through one or more uplinksubframes by using uplink transmission setting information received fromeNB is provided.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1 and 2 are diagrams illustrating a communication system accordingto an embodiment of the present disclosure;

FIG. 3 is a diagram illustrating a channel access scheme in the longterm evolution (LTE) standard according to an embodiment of the presentdisclosure;

FIG. 4 is a diagram illustrating a problem of a channel access scheme inthe LTE standard according to an embodiment of the present disclosure;

FIG. 5 is a diagram illustrating a channel access scheme according to anembodiment of the present disclosure;

FIG. 6 is a block diagram illustrating a structure of user equipment(UE) according to an embodiment of the present disclosure; and

FIG. 7 is a block diagram illustrating a structure of evolved NodeB(eNB) according to an embodiment of the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand configurations may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

For the same reason, some elements are exaggerated, omitted orschematically shown in the accompanying drawings. Also, the size of eachelement does not entirely reflect the actual size. In the drawings, thesame or corresponding elements are denoted by the same referencenumerals.

The advantages and features of the present disclosure and the manner ofachieving them will become apparent with reference to the embodimentsdescribed in detail below with reference to the accompanying drawings.The present disclosure may, however, be embodied in many different formsand should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of thepresent disclosure to those skilled in the art. To fully disclose thescope of the present disclosure to those skilled in the art, and thepresent disclosure is only defined by the scope of the claims. Likereference numerals refer to like elements throughout the specification.

It will be understood that each block of the flowchart illustrations,and combinations of blocks in the flowchart illustrations, may beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which are executed via the processor of the computer or otherprogrammable data processing apparatus, generate means for implementingthe functions specified in the flowchart block or blocks. These computerprogram instructions may also be stored in a computer usable orcomputer-readable memory that may direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks. The computer program instructions may also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that are executed on the computer or otherprogrammable apparatus provide steps for implementing the functionsspecified in the flowchart block or blocks.

And each block of the flowchart illustrations may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

The term “unit”, as used herein, may refer to a software or hardwarecomponent or device, such as a field programmable gate array (FPGA) orapplication specific integrated circuit (ASIC), which performs certaintasks. A unit may be configured to reside on an addressable storagemedium and configured to execute on one or more processors. Thus, amodule or unit may include, by way of example, components, such assoftware components, obj ect-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. The functionality provided for in the components andmodules/units may be combined into fewer components and modules/units orfurther separated into additional components and modules.

Hereinafter, a long term evolution (LTE) system and an LTE-advanced(LTE-A) system are exemplified in the present description, but thepresent disclosure may be applied to any other communication systemusing a licensed band (also referred to as a licensed spectrum or alicensed carrier) and an unlicensed band (also referred to as anunlicensed spectrum or an unlicensed carrier) without adding orsubtracting.

In general, the frequency band that is currently used in the LTE systemis the licensed band used by an operator having authority. However,since a typical frequency band (e.g., a frequency band of 5 GHz or less)that provides a mobile communication service has been already occupiedby another operator or another communication system, an operator mayoften fail to obtain a number of licensed band frequencies and thus havedifficulty in expanding the system capacity by using the carrieraggregation (CA) technology.

Therefore, in order to process rapidly increasing mobile data in anenvironment where it is difficult to secure a license band frequency asdescribed above, a technique for utilizing an LTE system in anunlicensed band (unlicensed spectrum or unlicensed carrier) has beenrecently studied (e.g., LTE in unlicensed (LTE-U), licensed-assistedaccess (LAA)). In particular, since the 5 GHz band in the unlicensedband is used by a relatively small number of communication devices incomparison with the 2.4 GHz unlicensed band and allows the utilizationof a very wide bandwidth, it is relatively easy to acquire an additionalfrequency band. In other words, using LTE technology that integrates anduses multiple frequency bands, namely, the CA technology, allows theutilization of licensed band and unlicensed band frequencies. In otherwords, by setting the LTE cell in the licensed band to PCell (or Pcell)and setting the LTE cell (LAA cell or LTE-U cell) in the unlicensed bandto SCell (or S cell or LAA SCell) by using the existing CA technology,the LTE system can be operated in the licensed and unlicensed bands. Inthis case, this system can be applied not only to a CA environment inwhich an ideal backhaul connects the licensed and unlicensed bands, butalso to a dual-connectivity environment in which a non-ideal backhaulconnects the licensed and unlicensed bands.

Normally, the LTE/LTE-A system transmits data using an orthogonalfrequency division multiple (OFDM) access transmission scheme. In theOFDM scheme, a modulated signal is located in two-dimensional resourcescomposed of time and frequency. The resources on the time axis aredistinguished by different OFDM symbols, which are orthogonal to eachother. The resources on the frequency axis are distinguished bydifferent subcarriers, which are also orthogonal to each other. That is,in the OFDM scheme, by designating a specific OFDM symbol on the timeaxis and designating a specific subcarrier on the frequency axis, asingle minimum unit resource referred to as a resource element (RE) canbe indicated. Different REs have characteristics orthogonal to eachother even though passing through a frequency selective channel, so thatsignals transmitted in different REs can be received at the receivingside theoretically without mutual interference. In the OFDM-based LTEcommunication system using a normal CP, a downlink bandwidth consists ofa plurality of resource blocks (RBs), and each physical resource block(PRB) may be composed of 12 subcarriers arranged along the frequencyaxis and 14 or 12 OFDM symbols arranged along the time axis. Here, thePRB is a basic unit of resource allocation.

A reference signal (RS) received from evolved node B (eNB) is a signalthat enables user equipment (UE) to perform channel estimation and, inthe LTE communication system, includes a common reference signal (CRS)and a demodulation reference signal (DMRS) as one of dedicated referencesignals. The CRS which is a reference signal transmitted over the entiredownlink band can be received by all UEs and is used for channelestimation, feedback information configuration of UE, or demodulation ofa control channel and a data channel. The DMRS which is also a referencesignal transmitted over the entire downlink band is used for channelestimation and data channel demodulation of specific UE and, unlike CRS,is not used for feedback information configuration. Therefore, the DMRSis transmitted through the PRB resource to be scheduled by the UE.

A subframe on the time axis is composed of two slots of 0.5 ms length,i.e., the first slot and the second slot. A physical dedicated controlchannel (PDCCH) region, which is a control channel region, and anenhanced PDCCH (ePDCCH) region, which is a data channel region, aredivided and transmitted on the time axis. This is for quickly receivingand demodulating a control channel signal. In addition, the PDCCH regionis located over the entire downlink band, and one control channel isdivided into control channels having smaller units and distributed inthe entire downlink band. The uplink is divided into a control channel(PUCCH) and a data channel (PUSCH). A response channel and the otherfeedback information for the downlink data channel are transmittedthrough the control channel if there is no data channel and to the datachannel if there is the data channel.

FIGS. 1 and 2 are diagrams illustrating a communication system accordingto an embodiment of the present disclosure.

Referring to FIGS. 1 and 2, FIG. 1 shows a case where an LTE cell 102and an LAA cell 103 coexist in a small eNB 101 in the network. UE 104transmits and receives data to and from the eNB 101 through the LTE cell102 and the LAA cell 103. There is no restriction on the duplex schemeof the LTE cell 102 or the LAA cell 103. It may be supposed that a cellwhich performs data transmission/reception operation using a licensedband is the LTE cell 102 or PCell and that a cell which performs datatransmission/reception operation using an unlicensed band is the LAAcell 103 or SCell. Although the uplink transmission may be limited toonly transmission through the LTE cell 102 when the LTE cell is PCell,the uplink transmission through the LAA cell 103 is also possible.

FIG. 2 shows an LTE macro eNB 211 for wide coverage and an LAA small eNB212 for an increase in data transmission installed in the network. Inthis case, there is no restriction on the duplex scheme of the LTE macroeNB 211 or the LAA small eNB 212. In this case, the LTE macro eNB 211may be replaced with an LTE small eNB (not shown). In addition, theuplink transmission may be set to be performed only through the LTEmacro eNB 211 when the LTE eNB is a PCell. At this time, it may besupposed that the LTE macro eNB 211 and the LAA small eNB 212 have idealbackhaul networks. In this case, faster X2 communication (X2 interface)213 between eNBs is allowed, so that the LAA small eNB 212 can receivein real time related control information from the LTE macro eNB 211through the X2 communication 213 even though the uplink transmission isperformed only to the LTE macro eNB 211. If there is a non-idealbackhaul network between the LTE macro eNB 211 and the LAA small eNB212, the uplink transmission of the UE 214 may be allowed through theLAA small eNB 212 because the faster X2 communication 213 is impossible.Proposals of the present disclosure are applicable to both the system ofFIG. 1 and the system of FIG. 2. In FIG. 2, the LAA cell 215 and the LTEcell 216 are shown in relation to the UE 214.

Meanwhile, a channel sensing operation defined as to transmission of adownlink data channel in the current LTE standard will be described asfollows, for example.

FIG. 3 is a diagram illustrating a channel access scheme in the LTEstandard according to an embodiment of the present disclosure.

FIG. 4 is a diagram illustrating a problem of a channel access scheme inthe LTE standard according to an embodiment of the present disclosure.

Referring to FIG. 3, in order to transmit a downlink control channel anda data channel to at least one UE through an unlicensed band channel, aresource access technique such as listen-before-talk (LBT) unlike theexisting licensed band should be considered. Namely, the eNB thatdesires to transmit a downlink control channel and a data channel to atleast one UE through an unlicensed band channel may determine whetherthe channel is in an idle state during at least one defer duration(T_(d)) 310 and N additional channel sensing slots (T_(sl)) 330. If itis determined that the channel is in an idle state during the at leastone defer duration 310 and N additional channel sensing slots 330, theeNB may occupy the unlicensed band channel and transmit the downlinkchannel 340 and 360.

In this case, the defer duration 310 and the additional channel sensingslot 330 may be defined differently according to a channel accesspriority class (p) of the data channel to be transmitted. Namely, thedefer duration 310 and the additional channel sensing slot 330 may bedefined depending on channel sensing and occupying durations accordingto the channel access priority class in Table 1 provided below. Forexample, the defer duration 310 may be formed of an idle slot duration(T_(f)) 315 and additional m_(p) channel sensing slots 320. In thiscase, the idle slot duration 315 may have at least 16 us in time. Also,each of the channel sensing slots 320 may be defined as at least 9 us.For example, when the channel access priority class (p) is 3 in Table 1,the defer duration (T_(d)) 310 which is the sum of the idle slotduration (T_(f)) 315 and the m_(p) channel sensing slots (m_(p)*T_(sl))320 may be set to 43 us (i.e., 16 us (T_(f))+3*9 us (m_(p)*T_(sl))).

The number (N) of the additional channel sensing slots 330 is a valueuniformly and randomly selected within a contention window size (CW_(p))with respect to the channel access priority (p) in Table 1. Namely, N isa value arbitrarily selected between 0 and the contention window size(CW_(p)). At this time, the contention window size (CW_(p)) may be equalto or greater than the minimum contention window size (CW_(min,p)) andequal to or smaller than the maximum contention window size (CW_(max,p))(namely, CW_(min,p)≤CW_(p)≤CW_(max,p)). For example, when the channelaccess priority class (p) is 3, the contention window size (CW_(p)) isselected between the minimum contention window size (CW_(min,p)), 15,and the maximum contention window size (CW_(max,p)), 63, and may be oneof 15, 31 and 63.

TABLE 1 Channel Access allowed Priority Class (p) m_(p) CW_(min, p)CW_(max, p) T_(mcot, p) CW_(p) sizes 1 1 3 7 2 ms {3, 7}  2 1 7 15 3 ms{7, 15} 3 3 15 63 8 or 10 ms {15, 31, 63} 4 7 15 1023 8 or 10 ms {15,31, 63, 127, 255, 511, 1023}

If the size of a signal received during the channel sensing duration 335formed of the at least one defer duration 310 and the N additionalchannel sensing slots 330 does not exceed an energy detection threshold(X_(thresh)), e.g., −62 dBm, the eNB may determine that the channel isin an idle state. Then the eNB may transmit a downlink control channeland a data channel to the UE through the channel 340 and 360 determinedas being in an idle state. At this time, the threshold used fordetermining, depending on the size of a received signal, that theunlicensed band channel is an idle channel may be set differently usingone or more of the type of a signal/channel to be transmitted, abandwidth for transmission, and transmission power. For example, in caseof low transmission power, the energy detection threshold which isrelatively higher than in case of high transmission power may be appliedto determine an idle state of the unlicensed band channel. If the sizeof a signal received by the eNB during the channel sensing duration 335which is set according to the channel access priority class does notexceed the above threshold (X_(thresh)), the eNB may continuously occupyand use the unlicensed band channel 340, 360 determined as an idle stateduring the maximum channel occupancy duration or time (T_(mcot) orT_(mcot,p)) which is set according to the channel access priority class(p). For example, if the eNB determines that the unlicensed band is inan idle state during the channel sensing duration 335 as to the channelaccess priority class (p) 3 in Table 1, the eNB may continuously occupythe channel without any channel sensing operation for 8 ms maximally.

In the above embodiment of the present disclosure, the maximum occupancytime (T_(mcot,p)) may be set differently according to frequency bands orregionally or nationally defined regulations. For example, in case ofJapan, the maximum occupancy time (T_(j)) in the unlicensed band of 5GHz band is currently regulated to 4 ms. On the other hand, in case ofEurope, it is possible to continuously occupy and use the channel up to10 ms or 13 ms. Therefore, if the maximum occupancy time (T_(mcot,p)) ofthe eNB or UE like the channel access priority class (p) 3 in Table 1 isgreater than the time defined by the regulations, the eNB or UE cannotuse the channel during the maximum occupancy time (T_(mcot,p)) definedat the channel access priority class. Accordingly, channel sensing andaccessing operations defined in the current LTE standard in order tosolve the above problem may be as follows (for example, in view of theeNB, the case of Japan, and the channel access priority class 3).

According to the channel access priority class (p) 3, the defer duration(T_(d)) 310 may be formed of at least 16 us time and three channelsensing slots 320. Also, the number (N) of additional channel sensingslots 330 is randomly selected from one of the contention window sizes{15, 31, 63 } allowed in the channel access priority class (p) 3. Inthis case, the contention window size (CW_(p)) used for determining thenumber of additional channel sensing slots 330 may be selected as one ofthe allowed contention window sizes {15, 31, 63 } (allowed CW_(p) sizes)in the channel access priority class (p) 3, depending on the resulthybrid automatic repeat request—acknowledgement (HARQ-ACK) or hybridautomatic repeat request—negative acknowledgement (HARQ-NACK)) ofreception of a data channel from the eNB or UE. Namely, if the size of asignal received during the channel sensing duration 335 formed of thedefer duration 310 set according to the channel access priority class(p) 3 and the N additional channel sensing slots 330 does not exceed theenergy detection threshold (X_(thresh)), e.g., −62 dBm, the eNB thatdesires to transmit a downlink control channel and a data channel to atleast one UE through an unlicensed band channel may determine that thechannel is in an idle state. Then the eNB may transmit a downlinkcontrol channel and a data channel through the channel determined asbeing in an idle state without any channel sensing operation for a time(T_(j)=4 ms for Japan) defined according to a region or nation.

In this case, if the maximum occupancy time (T_(mcot,p)=8 ms orT_(mcot,p)=10 ms) of the eNB or UE defined in the channel accesspriority class (p) (i.e., the maximum occupancy time which allows theeNB or the UE to maximally occupy an unlicensed band) is greater thanthe time (T_(j)=4 ms) defined by the regional or national regulation(i.e., an actual occupancy time which allows the eNB or the UE toactually occupy an unlicensed band), the eNB may perform channeltransmission during the time 340 (T_(j)=4 ms) defined by the regional ornational regulation. Then the eNB may perform again a channel sensingoperation in the additional channel sensing duration 350 (T_(js)=34 us).If the size of a signal received during the channel sensing duration 350does not exceed the energy detection threshold (X_(thresh)), e.g., −62dBm, the eNB may determine that the channel is in an idle state. Also,the eNB may further occupy the channel during the additional channeloccupying time 360. In this case, after the unlicensed band channel isdetermined as an idle channel in the channel sensing duration 335according to the channel access priority class (p), the sum of theinitial channel occupancy time 340, the additional channel sensingduration 350 and the additional channel occupancy time 360 cannot exceed1000·T_(mcot)+floor(t_(mcot)/T_(j))·T_(js) (us).

According to the scheme, defined in the LTE standard, if the maximumoccupancy time (T_(mcot,p)) of the eNB or UE defined in the channelaccess priority class (p) is 8 ms (T_(mcot,p)=8 ms) and if the maximumoccupancy time (T_(mcot,p)) is greather than the time (T_(j)=4 ms)defined by the regional or national regulation, the sum of the initialchannel occupancy time 340, the additional channel sensing duration 350and the additional channel occupancy time 360 after the unlicensed bandchannel is determined as an idle channel in the channel sensing duration335 according to the channel access priority class (p) becomes1000·T_(mcot)+floor(T_(mcot)/T_(j))·T_(js)=8 ms+68 us. Namely, the sumof the initial channel occupancy time 340, the additional channelsensing duration 350 and the additional channel occupancy time 360 is1000·T_(mcot)+floor(T_(mcot)/T_(j))·T_(js), which is obtained as 1000*8(us)+floor(8/4)*34 (us), namely, 8000+2*34 (us). Therefore, theadditional channel sensing duration (T_(js)) has two sections eachhaving the length of 34 us or has one section having the length of 68us.

In other words, according to the scheme, defined in the LTE standard, ifthe maximum occupancy time (T_(mcot,p)=8 ms or T_(mcot,p)=10 ms) of theeNB or UE is greater than the time (T_(j)=4 ms) defined by the regionalor national regulation, the eNB performs channel transmission during thetime 340 (T_(j)=4 ms) defined by the regional or national regulation andperforms again a channel sensing operation during the additional channelsensing duration (T_(js)) having the length of 34 us. In addition, ifthe maximum occupancy time (T_(mcot,p)) of the eNB or UE is 8 ms and ifthe time (T_(j)) defined by the regional or national regulation is 4 msor the like, the eNB performs again the channel sensing operation duringtwo additional channel sensing durations (T_(js)) each having the lengthof 34 us or one additional channel sensing duration (T_(js)) having thelength of 68 us.

Referring to FIG. 4, according to the currently defined LTE standard,even though it is determined that the channel is not an idle channel inthe first additional channel sensing duration 450 after the initialchannel occupancy time 440 as shown in FIG. 4, the eNB may furtherperform a channel sensing operation through the second additionalchannel sensing duration 455. The defer duration 410 may be formed of anidle slot duration (T_(f)) 415 and additional m_(p) channel sensingslots 420, as illustrated in FIG. 4.

Namely, if the size of a signal received during the channel sensingduration 435 including the defer duration 410 and the N additionalchannel sensing slots 430 is equal to or smaller than a predeterminedthreshold such as an energy detection threshold (X_(thresh)), the eNBmay determine that the channel is in an idle state. Then the eNB maytransmit a downlink control channel and a data channel to the UE throughthe channel determined as being in an idle state. The transmission timemay be possible up to the maximum occupancy time (T_(mcot,p)) of the eNBor UE defined in the channel access priority class (p). However, if themaximum occupancy time (T_(mcot,p)) of the eNB or UE defined in thechannel access priority class (p) is greater than the time (T_(j))defined by the regional or national regulation, the eNB may occupy anduse the channel during the initial channel occupancy time 440 whichcorresponds to the time (T_(j)) defined by the regional or nationalregulation. Also, the eNB may perform again a channel sensing operationduring the additional channel sensing durations 450 and 455 and, if thesize of a signal received during the additional channel sensingdurations 450 an 455 is equal to or smaller than the threshold(X_(thresh)), determine that the channel is in an idle state. Then theeNB may occupy and use the channel during the additional channeloccupancy time 460. In this case, if it is defined that the sum of theinitial channel occupancy time 440, the additional channel sensingdurations 450 and 455 and the additional channel occupancy time 460cannot exceed 1000·T_(mcot)+floor(T_(mcot)/T_(j))·T_(js) (us), theadditional channel sensing duration (T_(js)) may include two sections450 and 455 each of which has the length of 34 us as discussed above.Thus, even though the first additional channel sensing duration 450after the initial channel occupancy time 440 is not an idle channel, theeNB may further perform the channel sensing operation through the secondadditional channel sensing duration 455.

FIG. 5 is a diagram illustrating a channel access scheme according to anembodiment of the present disclosure.

Referring to FIG. 5, in order to solve the above problem in anembodiment of the present disclosure, if the maximum occupancy time(T_(mcot,p)) of the eNB or UE defined in the channel access priorityclass (p) is greater than the time (T_(j)) defined by the regional ornational regulation, the eNB determines that the unlicensed band channelis an idle channel, through a channel sensing operation performed duringthe channel sensing duration 535 set according to the channel accesspriority class (p), and then defines that the sum of the initial channeloccupancy time 540, the additional channel sensing duration 550 (T_(js))and the additional channel occupancy time 560 cannot exceed1000·T_(mcot)+(ceil(T_(mcot)/T_(j))−1)·T_(js) (us) or1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (us).

Specifically, the eNB that desires to transmit a downlink controlchannel and a data channel to at least one UE through the unlicensedband channel, or the UE that desires to transmit an uplink controlchannel or a data channel to eNB through the unlicensed band channel,establishes the channel access priority class (p) defined according tothe control channel or data channel to be transmitted (or according tothe type of information to be sent, e.g., VoIP, FTP, or the like).

Also, if the size of a signal received from the eNB or UE during thechannel sensing duration 535 formed of the defer duration 510 definedaccording to the channel access priority class (p) and the N additionalchannel sensing slots 530 selected randomly in the contention windowdefined according to the channel access priority class (p) does notexceed the energy detection threshold (X_(thresh)), e.g., −62 dBm or −72dBm, the eNB or UE may determine that the channel is in an idle state.At this time, the defer duration 510 may include the idle slot duration515 having the length of, for example, 16 us and m_(p) channel sensingslots 520. Each of the channel sensing slots 520 may have the length of,for example, 9 us.

Also, the eNB or UE may occupy the unlicensed band channel and transmita downlink signal or an uplink signal to the UE or eNB. In this case,the eNB or UE may continuously occupy the unlicensed band and transmit asignal during the minimum time between the maximum channel occupancytime (T_(mcot,p)) defined according to the channel access priority classand the time (T_(j)=4 ms for Japan) defined according to regions ornations as to the unlicensed band.

If the maximum occupancy time (T_(mcot,p)=8 ms or T_(mcot,p)=10 ms) ofthe eNB or UE defined in the channel access priority class (p) isgreater than the time (T_(j)=4 ms) defined by the regional or nationalregulation, the eNB may occupy the channel and transmit a signal duringthe time 540 (T_(j)=4 ms) defined by the regional or nationalregulation. Then, after the initial channel occupancy time 540 (or thefirst channel occupancy time) corresponding to the time 540 (T_(j)=4 ms)defined by the regional or national regulation, the eNB or UE mayperform again a channel sensing operation in the additional channelsensing duration 550 (T_(js)=34 us). If the size of a signal receivedduring the channel sensing duration 550 does not exceed the energydetection threshold (X_(thresh)), e.g., −62 dBm or −72 dBm, the eNB maydetermine that the channel is in an idle state, and further occupy thechannel.

In this case, after the unlicensed band channel is determined as an idlechannel in the channel sensing duration 535 according to the channelaccess priority class (p), the sum of the initial channel occupancy time540, the additional channel sensing duration 550 and the additionalchannel occupancy time 560 is defined so as not to exceed1000·T_(mcot)+(ceil(T_(mcot)/T_(j))−1)·T_(js) (us) or1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (us). In this case, if themaximum occupancy time (T_(moct,p)) of the eNB or UE defined in thechannel access priority class (p) is 8 ms (T_(mcot,p)=8 ms) and if themaximum occupancy time (T_(mcot,p)) is greater than the time (T_(j)=4ms) defined by the regional or national regulation, the sum of theinitial channel occupancy time 540, the additional channel sensingduration 550 and the additional channel occupancy time 560 after theunlicensed band channel is determined as an idle channel in the channelsensing duration 535 according to the channel access priority class (p)becomes 1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js), which is obtainedas 1000*8 (us)+ceil(8/4−1)*34 (us), namely, 8000+34 (us).

In this case, the additional channel sensing duration 550 may apply atleast one method between a channel sensing operation in the same way asa m_(p) value is 2 in defer duration (T_(d)) 510 of FIG. 5 and a channelsensing operation in one continuous duration such as the additionalchannel sensing duration 350 of FIG. 3. For example, the additionalchannel sensing duration 550 may include the idle slot duration 555having the length of 16 us and the two channel sensing slots 557 (2*9us).

If the maximum channel occupancy time (T_(mcot,p)) defined according tothe channel access priority class (p) is 10 ms, it is possible tomaximally utilize the maximum channel occupancy time, 10 ms, definedaccording to the channel access priority class (p) through two channelsensing durations 535 and 550 and two channel occupancies, the initialchannel occupancy time 540 and the additional channel occupancy time 560by applying the above method.

FIG. 6 is a block diagram illustrating a structure of UE according to anembodiment of the present disclosure.

Referring to FIG. 6, the UE according to an embodiment of the presentdisclosure may include a transceiver 610 and a controller 620.

The transceiver 610 may transmit and/or receive a signal to or fromother network entities.

The controller 620 may control the UE to perform operations discussed inthe above embodiments. For example, the controller 620 may control thetransceiver 610 to receive data from eNB through a licensed band, and ifan unlicensed band channel is in an idle state during a first channelsensing duration, to control the transceiver 610 to receive data fromthe eNB through an unlicensed band during a first channel occupyingduration, a second channel sensing duration, and a second channeloccupying duration.

Meanwhile, the controller 620 and the transceiver 610 are notnecessarily implemented as separate devices, but may be implemented as asingle unit in the form of a single chip. In addition, the controller620 and the transceiver 610 may be electrically connected to each other.

Additionally, for example, the controller 620 may be a circuit, anapplication-specific circuit, or at least one processor. In addition,the operations of the UE may be realized by providing a memory unit forstoring a corresponding program code to the UE. That is, the controller620 may execute the above-described operations by reading and executingthe program code stored in the memory unit by a processor or a centralprocessing unit (CPU).

FIG. 7 is a block diagram illustrating a structure of eNB according toan embodiment of the present disclosure.

Referring to FIG. 7, the eNB according to an embodiment of the presentdisclosure may include a transceiver 710 and a controller 720 (at leastone processor).

The transceiver 710 may transmit and/or receive a signal to or fromother network entities.

The controller 720 may control the eNB to perform operations discussedin the above embodiments. For example, the controller 720 may controlthe transceiver 710 to transmit data to UE through a licensed band, todetermine whether an unlicensed band channel is in an idle state duringa first channel sensing duration, and if the unlicensed band channel isin the idle state, to control the transceiver 710 to transmit data tothe UE through an unlicensed band during a first channel occupyingduration, a second channel sensing duration, and a second channeloccupying duration.

Meanwhile, the controller 720 and the transceiver 710 are notnecessarily implemented as separate devices, but may be implemented as asingle unit in the form of a single chip. In addition, the controller720 and the transceiver 710 may be electrically connected to each other.

Additionally, for example, the controller 720 may be a circuit, anapplication-specific circuit, or at least one processor. In addition,the operations of the eNB may be realized by providing a memory unit forstoring a corresponding program code to the eNB. That is, the controller720 may execute the above-described operations by reading and executingthe program code stored in the memory unit by a processor or a centralprocessing unit (CPU).

The various elements, modules, etc. of entities, such as eNB or UE,disclosed herein may be implemented in a hardware circuit, e.g., acomplementary metal oxide semiconductor based logic circuit, firmware,software, and/or a combination thereof embedded in a machine-readablemedium. In one example, the various electrical structures and methodsmay be implemented using electrical circuits such as transistors, logicgates, and custom semiconductors.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for communication of a base station, themethod comprising: determining whether an unlicensed band channel of anunlicensed band is in an idle state during a first channel sensingduration according to a channel access priority class; transmitting datato a terminal through the unlicensed band during a first channeloccupying duration, in case that the unlicensed band channel of theunlicensed band is in the idle state during the first channel sensingduration; identifying that the first channel occupying duration is lessthan a maximum occupancy time possible for the base station or theterminal to continuously occupy the unlicensed band according to thechannel access priority class, and the first channel occupying durationis equal to an actual occupancy time allowed for the base station or theterminal to continuously occupy the unlicensed band according to aregional policy or a national policy; determining whether the unlicensedband channel of the unlicensed band is an idle state during a secondchannel sensing duration; and transmitting the data to the terminalthrough the unlicensed band during a second channel occupying duration,in case that the unlicensed band channel of the unlicensed band is inthe idle state during the second channel sensing duration, wherein a sumof the first channel occupying duration, the second channel sensingduration, and the second channel occupying duration is equal to or lessthan a certain time determined based on a rounding up value of a resultof a calculation between the maximum occupancy time and the actualoccupancy time.
 2. The method of claim 1, wherein the channel accesspriority class includes 3 or
 4. 3. The method of claim 1, wherein thecalculation includes dividing the maximum occupancy time by the actualoccupancy time and then subtracting one.
 4. The method of claim 1,wherein the certain time is determined according to1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (μss), wherein T_(mcot)denotes the maximum occupancy time possible for the base station or theterminal to continuously occupy the unlicensed band, wherein T_(j)denotes the actual occupancy time allowed for the base station or theterminal to continuously occupy the unlicensed band, and wherein T_(js)denotes a length of the second channel sensing duration.
 5. The methodof claim 1, wherein the second channel sensing duration includes: anidle slot duration including 16 82 s, and two channel sensing slotdurations each including 9 μs.
 6. A method for communication of aterminal, the method comprising: receiving data from a base stationthrough an unlicensed band during a first channel occupying duration, incase that an unlicensed band channel of the unlicensed band is in anidle state during a first channel sensing duration according to achannel access priority class; and receiving, when the first channeloccupying duration is less than a maximum occupancy time possible forthe base station or the terminal to continuously occupy the unlicensedband according to the channel access priority class and the firstchannel occupying duration is equal to an actual occupancy time allowedfor the base station or the terminal to continuously occupy theunlicensed band according to a regional policy or a national policy, thedata from the base station through the unlicensed band during a secondchannel occupying duration, in case that the unlicensed band channel ofthe unlicensed band is in an idle state during a second channel sensingduration, wherein a sum of the first channel occupying duration, thesecond channel sensing duration, and the second channel occupyingduration is equal to or less than a certain time determined based on arounding up value of a result of a calculation between the maximumoccupancy time and the actual occupancy time.
 7. The method of claim 6,wherein the channel access priority class includes 3 or
 4. 8. The methodof claim 6, wherein the calculation includes dividing the maximumoccupancy time by the actual occupancy time and then subtracting one. 9.The method of claim 6, wherein the certain time is determined accordingto 1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (μs), wherein T_(mcot)denotes the maximum occupancy time possible for the base station or theterminal to continuously occupy the unlicensed band, wherein T_(j)denotes the actual occupancy time allowed for the base station or theterminal to continuously occupy the unlicensed band, and wherein T_(js)denotes a length of the second channel sensing duration.
 10. The methodof claim 6, wherein the second channel sensing duration includes: anidle slot duration including 16 μs, and two channel sensing slotdurations each including 9 μs.
 11. A base station comprising: atransceiver; and a controller configured to: determine whether anunlicensed band channel of an unlicensed band is in an idle state duringa first channel sensing duration according to a channel access priorityclass, control the transceiver to transmit data to a terminal throughthe unlicensed band during a first channel occupying duration, in casethat the unlicensed band channel of the unlicensed band is in the idlestate during the first channel sensing duration, identify that the firstchannel occupying duration is less than a maximum occupancy timepossible for the base station or the terminal to continuously occupy theunlicensed band according to the channel access priority class, and thefirst channel occupying duration is equal to an actual occupancy timeallowed for the base station or the terminal to continuously occupy theunlicensed band according to a regional policy or a national policy,determine, whether the unlicensed band channel of the unlicensed band isan idle state during a second channel sensing duration, and control thetransceiver to transmit the data to the terminal through the unlicensedband during a second channel occupying duration, in case that theunlicensed band channel of the unlicensed band is in the idle stateduring the second channel sensing duration, wherein a sum of the firstchannel occupying duration, the second channel sensing duration, and thesecond channel occupying duration is equal to or less than a certaintime determined based on a rounding up value of a result of acalculation between the maximum occupancy time and the actual occupancytime.
 12. The base station of claim 11, wherein the channel accesspriority class includes 3 or
 4. 13. The base station of claim 11,wherein the calculation includes dividing the maximum occupancy time bythe actual occupancy time and then subtracting one.
 14. The base stationof claim 11, wherein the certain time is determined according to1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (μs), wherein T_(mcot)denotes the maximum occupancy time possible for the base station or theterminal to continuously occupy the unlicensed band, wherein T_(j)denotes the actual occupancy time allowed for the base station or theterminal to continuously occupy the unlicensed band, and wherein T_(js)denotes a length of the second channel sensing duration.
 15. The basestation of claim 11, wherein the second channel sensing durationincludes: an idle slot duration including 16 us, and two channel sensingslot durations each including 9 us.
 16. A terminal comprising: atransceiver; and a controller configured to: control the transceiver toreceive data from a base station through an unlicensed band during afirst channel occupying duration, in case that an unlicensed bandchannel of the unlicensed band is in an idle state during a firstchannel sensing duration according to a channel access priority class,and control the transceiver to receive, when the first channel occupyingduration is less than a maximum occupancy time possible for the basestation or the terminal to continuously occupy the unlicensed bandaccording to the channel access priority class and the first channeloccupying duration is equal to an actual occupancy time allowed for thebase station or the terminal to continuously occupy the unlicensed bandaccording to a regional policy or a national policy, the data from thebase station through the unlicensed band during a second channeloccupying duration, in case that the unlicensed band channel of theunlicensed band is in an idle state during a second channel sensingduration, wherein a sum of the first channel occupying duration, thesecond channel sensing duration, and the second channel occupyingduration is equal to or less than a certain time determined based on arounding up value of a result of a calculation between the maximumoccupancy time and the actual occupancy time.
 17. The terminal of claim16, wherein the calculation includes dividing the maximum occupancy timeby the actual occupancy time and then subtracting one.
 18. The terminalof claim 16, wherein the certain time is determined according to1000·T_(mcot)+ceil(T_(mcot)/T_(j)−1)·T_(js) (μs), wherein T_(mcot)denotes the maximum occupancy time possible for the base station or theterminal to continuously occupy the unlicensed band, wherein T_(j)denotes the actual occupancy time allowed for the base station or theterminal to continuously occupy the unlicensed band, and wherein T_(js)denotes a length of the second channel sensing duration.
 19. Theterminal of claim 16, wherein the second channel sensing durationincludes: an idle slot duration including 16 μs, and two channel sensingslot durations each including 9 μs.
 20. The terminal of claim 16,wherein the channel access priority class includes 3 or 4.